Sulphur is a contact fungicide. Really there are two forms of sulphur fungicide: powder or soluble. I assume that you need only the soluble one. "Contact fungicide" mean that you can test just few parts of the plant, and you can see if there are some problems with the plant.
As pnut wrote in comment, I think the interpretation is that it can damage some other plants. In any case it is very widely used, for plants, orchards, vineyards, vegetables and garden. So it is not common to have problems with sulphur. But as far I know, some fruits (as plant part) doesn't like it (e.g. some apple's varieties).
So check to buy just sulphur (the kind that dissolve in water). It is cheap. Many other fungicides includes it: because it is cheap, and because it prevent resistance, but better to avoid them, if there are no needed.
But you should read carefully the instructions. There are temperature limits (minimum and maximum). Outside such temperatures, the sulphur could burn the leaves.
EDIT:
I find only the following sensitivity on Sulphur:
- high temperature: all plants
- Apple varieties: Golden Delicious, Imperatore, Jonathan, Rome Beauty, Stayman
- Pears: Williams
- some peaches and most apricots.
If I remember correctly the problems are just in fruits (and just fruits that are subject to "rust")
